Where is Cosine based and what areas do you cover?

Cosine Electrical is based at Waerenga in the North Waikato, between Te Kauwhata and Morrinsville. We cover the wider Waikato and South Auckland — from Manukau down to Te Awamutu, east to Thames, west to Raglan. Drive times from Waerenga: Hamilton 30-40 minutes, Cambridge 40 minutes, Pukekohe 30 minutes, Manukau 45 minutes, Raglan 75 minutes, Thames 60 minutes.

What is the digger operator on the crew thing?

Most electricians sub-contract digging for underground work — second contractor, second quote, second site visit. Cosine has a skilled digger operator on the crew, so for underground jobs we trench our own runs. One quote, one team, one site visit. Note: Cosine is not a registered drainlayer. Wastewater and stormwater scope sits with a licensed drainlayer.

How quickly do you get back with a quote?

Within 24 hours of the site visit. Itemised, in writing, valid 30 days. For smaller jobs we can often give a rough indication over the phone if you text photos of the existing setup.

What does a switchboard upgrade cost?

A straight switchboard upgrade in an average three-bedroom Waikato house is typically $1,500-$2,500 plus GST for board and labour. Push-ups: old cable failing insulation tests, mains upgrade needed (lines company involvement), asbestos in the meter-box backing board common in 60s and 70s houses. Everything flagged in the written quote — no surprises on the invoice.

What does an EV charger install cost?

Standard install with the existing switchboard up to spec is $1,200-$1,800 plus GST plus the charger. Older home needing a board upgrade adds $1,500-$2,500. Long trenched runs to a detached garage on a lifestyle block typically $2,500-$4,500 all-in.

Do you do compliance testing for landlords?

Yes — landlord WOF-equivalent inspections, RCD function tests, written reports with photos and plain-English findings. Insurance-ready paperwork.

Do you work with builders on renovations?

Yes — preferred sparky for several builders across Hamilton, Cambridge and Pukekohe. We walk through with the homeowner and builder before quoting, mark up the plans, and work to the builder's schedule. We don't hold up the next trade.

Can you handle commercial maintenance for property managers?

Yes — scheduled maintenance contracts, emergency callouts, fault-finding, compliance reporting. One number, one paperwork system, no padded packages and no lock-ins.

Do you certify the work?

Always. Every new circuit and every board upgrade gets a Certificate of Compliance emailed through within a day of the job finishing. Required for insurance, future sale and any audit.

What if you cannot fix a fault in one visit?

Some faults like earth leakage on a circuit shared by multiple cables genuinely need a second visit. Day 1 we isolate the faulty section onto its own RCBO so the rest of the house keeps power. Day 2 we test and replace the bad section. We don't punch holes in walls to brute-force the search.

Generator Changeover Switches: Keeping the Power On in Rural Waikato

Kris Goff

7 hours ago

3 min read

Short answer: to run your house off a generator you need a changeover switch wired in at the switchboard by a registered electrician. It physically prevents the generator and the network supply from ever being connected at the same time. Without one you cannot power fixed circuits safely, and back-feeding the network can kill a lineman working to restore your power.

Why a lead into a socket is not a solution

The arrangement people describe as a suicide cord - a lead with plugs on both ends, generator into a wall socket - does two dangerous things. It energises the house wiring through a circuit that is not protected for it, and it pushes power back out through your service line into the network. The transformer down the road steps that back up. Somebody working on what they have isolated as a dead line is then working on a live one. It is illegal, and it is the kind of illegal that kills other people.

What a proper setup looks like

A changeover switch at or next to the switchboard. Manual is fine and is what most rural houses have - you walk out, start the generator, throw the switch.
A generator inlet - a proper external appliance inlet, weatherproof, positioned where you will actually run the generator.
An essential services sub-board, so the generator feeds the circuits that matter rather than trying to carry the whole house.
Earthing done correctly for a portable generator. This is the part most DIY setups get wrong, and it is the part that protects you.
Testing and a Certificate of Compliance. It is fixed wiring, so it is prescribed electrical work.

What to put on the essential circuits

Fridge and freezer. The whole reason most people buy a generator.
The water pump. On tank or bore supply, no power means no water and no toilet.
Lighting to the kitchen, hallway and bathroom.
A few sockets for phone charging, the router and a heater.
The wood burner fan or a heat pump, if the generator has the capacity.
On a farm: the effluent pump and enough of the shed to get through a milking.

Leave off the range, the hot water cylinder and anything with a big motor unless you have specifically sized for them. Motors draw several times their running current at start-up, which is what stalls an undersized generator.

Sizing it

Add up the running load of your essential circuits, then allow headroom for the largest motor starting. A water pump is usually that motor. It is better to have a slightly larger generator and run it lightly loaded than to have one that stalls every time the pump kicks in. We will work out the number with you before you buy - it is a much cheaper conversation than the exchange.

Questions we get asked

Manual or automatic changeover?

Manual for most rural houses - simpler, cheaper, and you are usually home when it matters. Automatic makes sense where the outage cannot be attended, or where something like a freezer room or a farm system cannot wait.

Can I use the generator I already have?

Usually. We check the output, the outlet type, and how it is earthed, then size the inlet and the changeover to suit.

Does it work with solar and a battery?

Different setup, and it depends on the inverter. Some hybrid inverters have their own backup output that does the isolation for you. Tell us what you have got.

How often should I run it?

Start it monthly and run it under load. Generators fail from sitting still far more often than from working.

Getting it installed

We cover the rural Waikato and South Auckland from Waerenga - Te Kauwhata, Huntly, Ngaruawahia, Morrinsville, Paeroa, Thames, and north to Tuakau and Pukekohe. Call Kris on 021 466 666, or see the mains and switchboards page.